1. Field of the Invention
The present invention relates to a reed valve that limits a flow direction of fluid to only one direction using a resiliently deformable reed having a thin plate shape.
2. Description of Related Art
A conventional technology of a reed valve will be described in reference to FIGS. 5A and 5B. A reed valve 11 includes a valve plate 13 that has an opening 12 passing through the plate 13 in its thickness direction, and a resiliently deformable reed 14 that opens and closes the opening 12. (i) When a pressure in a valve closing direction (downward pressure in FIG. 5B) from one side of the valve plate 13 (upper side in FIG. 5B) toward the valve plate 13 is applied to the valve 11, the reed 14 is closely-attached on the valve plate 13 around the opening 12 to close the opening 12 (valve-closed); and (ii) Conversely, when a pressure in a valve opening direction (upward pressure in FIG. 5B) from the other side of the valve plate 13 (lower side in FIG. 5B) toward the valve plate 13 is applied to the valve 11, the reed 14 is resiliently deformed to open the opening 12 (valve-open).
At the time of valve closing, the reed 14 closes the opening 12 upon application of the pressure in the valve closing direction to the reed 14. Accordingly, if the pressure in the valve closing direction is large, a load applied to the reed 14 becomes large, so that the reed 14 may be greatly deformed. In such a case, (i) the reed 14 sinks toward the inside of the opening 12, and a sealed state of the opening 12 cannot thereby be maintained; (ii) the reed 14 does not return to its normal position as a result of sinking of the reed 14 inward of the opening 12; or (iii) defects (e.g., plastic deformation) may be caused in the reed 14 due to increase of the deformation of the reed 14. Therefore, as illustrated in FIGS. 5A and 5B, the reed valve 11 that prevents the defects such as the above-described (i) to (iii) by providing a supporting column 16 passing across the opening 12 inward of a frame part 15 is proposed.
Problems of the conventional technology will be described. The load in the valve closing direction that the reed 14 receives is applied greatly to a part of the valve 11 whose contact area with the reed 14 is large. Accordingly, in the case of the conventional technology, where a frame seating surface 15a of the frame part 15 with which the reed 14 is engaged, and a column seating surface 16a of the supporting column 16 with which the reed 14 is engaged, are formed in the same plane, a greater load is applied to to the supporting column 16 having a larger contact area with the reed 14, as indicated by a difference between sizes of white arrows in FIG. 5B (A).
On the other hand, since the frame part 15 of the valve plate 13 is fixed and supported by a fixing member, strength of the frame part 15 is increased by the fixing member. Accordingly, despite the application of the load in the valve closing direction to the frame part 15 by the reed 14, stress concentration on the frame part 15 is mitigated. However, strength of the supporting column 16 is not increased as with the frame part 15 because the supporting column 16 is provided inward of the frame part 15. Thus, upon application of the load in the valve closing direction by the reed 14, the stress concentration is generated particularly on the supporting column 16 on a central side of the opening 12 (B).
As described in the above (A) (B), when the load in the valve closing direction is applied by the reed 14, a greater load acts on the supporting column 16, and the stress concentration is caused on the central side of the supporting column 16. As a result, the supporting column 16 is subject to fracture. In JP-UM-A-H05-089876, a technology whereby part of a seating surface of a valve plate is caved in so as to reduce a contact area between a reed and the valve plate is disclosed for the technology relating to the reed valve. However, the technology described in JP-UM-A-H05-089876 decreases adhesive force of a contact surface between the reed and the valve plate by the reduction of the contact area between the reed and the valve plate, so as to facilitate the valve-opening by the reed. Therefore, this technology has a completely different objective from the present invention.